The present invention relates to methods and apparatus for handling and transporting a unit load including at least one container or the like and which are particularly suited for use in connection with handling and transporting the load between a ro/ro vessel and a terminal.
More particularly, the present invention relates to methods and apparatus for handling and transporting a load through the use of load transporting apparatus which are moveable on wheels along a ground surface and which are provided with a load handling system for taking-up the load from and then depositing the load on the ground surface.
According to the so-called ro/ro method, a load is transported into a vessel and out therefrom in a substantially horizontal plane by wheeled apparatus. Such method is economical and provides a high load handling capacity by virtue of the use of large load units, such as containers, as well as pallets, roll trailers, trailers, etc. Various types of machines have been utilized for handling the cargo sorted into the units described above, the most common including tow trucks for the roll trailers and trailers, and straddle trucks for the containers, pallets, fork lift trucks, etc.
Such arrangements are not entirely satisfactory, however, in that when the containers, open pallets or the like are transported by a roll trailer, a separate step is necessary for loading the container or pallet onto the roll trailer and, similarly, to unload the container or pallet from the roll trailer. A separate crane or truck is required for this operation in order to lift the containers. Of course, the roll trailer or load pallet constitutes an additional mass which must be transported which is still another drawback of the conventional arrangements. Moreover, the pallets, roll trailers and other load handling equipment of this type must be provided in numbers equivalent to three times the cargo capacity of the vessel thereby representing a significant capital cost.
The various drawbacks described above can be avoided by providing a load handling arrangement wherein the conventional tow truck and roll trailer combinations or other separate transporting apparatus are replaced by equipment which itself is adapted to effect the loading and unloading operations for the load transported thereby. Such self-loading vehicles and trailers of this type are commonly employed in road transport operations as well as in connection with the transporting of containers. For example, in one conventional arrangement of this type, containers to be transported are either loaded or taken-up from the ground by hauling the same onto a transporting vehicle using a wire or chain-type pulling apparatus which is attached to the end of the container. Such arrangements utilize a so-called exchangeable platform principle and are disclosed, for example, in Finnish Pat. No. 55 313. Additionally, arrangements are known wherein the containers are placed upon legs or suitably designed load platforms and are taken-up therefrom by a transporting vehicle which has been driven under the load, the height of the load space of the vehicle being adjustable, e.g., pneumatically or hydraulically. Arrangements of this type are illustrated in, for example, Finnish Pat No. 55 628 and U.S. Pat. No. 4,053,072. Moreover, arrangements of the latter type may include moveable bogies or separate bogies provided with a lifting shape, in order to increase their flexibility. In this connection, reference is made to U.S. Pat. No. 3,719,299.
However, although the self-loading arrangements of the type described above are well suited for road transport over relatively long distances, such arrangements are not efficient in applications where the load is transported over relatively short distances such, for example, as in the case of terminal applications. Thus, in such applications the mooring time of the vessel is necessarily short and for this reason the ro/ro arrangements described above are required in order to effect the loading and unloading of the containers in a short time and in order to facilitate the handling of the load in cramped spaces.